The post-genomics phase in the life sciences arena has brought an increased yield of new small molecules that are pursued to target particular diseases based on the new understanding of the molecular basis of disease. The tremendous progress achieved in molecular structural biology has allowed the identification and de novo design of efficient molecules or so called “smart drugs.” The new technologies based on the unraveling of the human genome, the intensive progress in elucidating the structures of the enzymes encoded therein combined with the efficiencies of combinatorial chemistry will continue to generate small molecules that need to be administered to patients in efficient and organoliptically acceptable forms. One aspect associated with ameliorating the effects of ingesting molecules that are generally unpalatable is to provide the drug in dosage forms, such as tablets and lozenges, which, when ingested, quickly dissolve in the mouth.
Tablets may be defined as solid dosage pharmaceutical forms containing drug substances with or without suitable fillers. They are produced by compression or compaction of a formulation containing the drug and certain excipients selected to aid in the processing and to improve the properties of the product. Tablets may be coated or uncoated and are made from powdered, crystalline materials. They may include various diluents, binders, disintegrants, lubricants, glidants and in many cases, colorants. Excipients used are classified according to the function they perform. For example, a glidant may be used to improve the flow of powder blend in the hopper and into the tablet die.
There has been widespread use of tablets since the latter part of the 19.sup.th century and the majority of pharmaceutical dosage forms are marketed as tablets. Major reasons of tablet popularity as a dosage form among pharmaceutical manufacturers are simplicity, low cost, and the speed of production. Other reasons include stability of drug product, convenience in packaging, shipping, and dispensing. To the patient or consumer, tablets offer convenience of administration, ease of accurate dosage, compactness, portability, blandness of taste, ease of administration, and elegant distinctive appearance.
Tablets may be plain, film or sugar coated, bisected, embossed, layered, or sustained release. They can be made in a variety of sizes, shapes and colors. Tablets may be swallowed, chewed, or dissolved in the buccal cavity or beneath the tongue. They may be dissolved in water for local or topical application. Sterile tablets are normally used for parenteral solutions and for implantation beneath the skin.
In addition to the active or therapeutic ingredients, tablets may contain a number of inert materials known as excipients. They may be classified according to the role they play in the final tablet. The primary composition includes a filler, binder, lubricant, and glidant. Other excipients which give physical characteristics to the finished tablet are coloring agents, and flavors in the case of chewable tablets. Without excipients most drugs and pharmaceutical ingredients cannot be directly compressed into tablets. This is primarily due to the poor flow and cohesive properties of most drugs. Typically, excipients are added to a formulation to impart good flow and compression characteristics to the material being compressed. Such properties are imparted to these excipients through pretreatment steps such as wet granulation, slugging, spray drying spheronization, or crystallization.
Lubricants are typically added to prevent the tableting materials from sticking to punches, minimize friction during tablet compression, and allow for removal of the compressed tablet from the die. Such lubricants are commonly included in the final tablet mix in amounts usually less than 1% by weight.
In addition, tablets often contain diluents which are added to increase the bulk weight of the blend resulting in a practical size for compression. This is often necessary where the dose of the drug is relatively small.
Another commonly used class of excipients in tablets is binders. Binders are agents, which impart cohesive qualities to the powdered material. Commonly used binders include starch, and sugars such as sucrose, glucose, dextrose, and lactose.
Disintegrants are often included to ensure that the tablet has an acceptable rate of disintegration. Typical disintegrants include starch derivatives and salts of carboxymethylcellulose.
Other desirable characteristics of excipients include the following:                High compressibility to allow strong tablets to be made at low compression forces.        Good flow properties that can improve the flow of other excipients in the formula.        Cohesiveness (to prevent tablet from crumbling during processing, shipping and handling).        
The three processes for making compressed tablets are wet granulation, direct compression, and dry granulation (slugging or roller compaction). The method of preparation and type of excipients are selected to give the tablet formulation the desired physical characteristics that allow for the rapid compression of the tablets. After compression, the tablets must have a number of additional attributes such as appearance, hardness, disintegrating ability, and an acceptable dissolution profile. Choice of fillers and other excipients will depend on the chemical and physical properties of the drug, behavior of the mixture during processing, and the properties of the final tablets. Preformulation studies are done to determine the chemical and physical compatibility of the active component with proposed excipients.
The properties of the drug, its dosage forms, and the economics of the operation will determine selection of the best process for tableting. Generally, both wet granulation and direct compression are used in developing a tablet.
The dry granulation method may be used where one of the constituents, either the drug or the diluent, has sufficient cohesive properties to be tableted. The method consists of blending, slugging the ingredients, dry screening, lubrication, and compression.
The wet granulation method is used to convert a powder mixture into granules having suitable flow and cohesive properties for tableting. The procedure consists of mixing the powders in a suitable blender followed by adding the granulating solution under shear to the mixed powders to obtain a granulation. The damp mass is then screened through a suitable screen and dried by tray drying or fluidized bed drying. Alternately, the wet mass may be dried and passed through a mill. The overall process includes: weighing, dry powder blending, wet granulating, drying, milling, blending lubrication and compression.
In general, powders do not have sufficient adhesive or cohesive properties to form hard, strong granules. A binder is usually required to bond the powder particles together due to the poor cohesive properties of most powders. Heat and moisture sensitive drugs cannot usually be manufactured using wet granulation. The large number of processing steps and processing time are problems due to high level manufacturing costs. Wet granulation has also been known to reduce the compressibility of some pharmaceutical excipients such as microcrystalline cellulose.
Direct compression is regarded as a relatively quick process where the powdered materials are compressed directly without changing the physical and chemical properties of the drug. The active ingredient(s), direct compression excipients and other auxiliary substances, such as a glidant and lubricant are blended in a twin shell blender or similar low shear apparatus before being compressed into tablets. This type of mixing was believed to be essential in order to prepare “pharmaceutically acceptable” dosage forms. For example, Remington's Pharmaceutical Sciences (RPS), pp 1203 to 1932 17.sup.th edition (1985), cautions pharmaceutical scientists that the manner in which a lubricant is added to a formulation must be carefully controlled.
Accordingly, lubricants are usually added to a granulation by gentle mixing. RPS warns that prolonged blending of a lubricant with a granulation can materially affect hardness and disintegration time for the resulting tablets. Furthermore, Ansel et al (1995) Pharmaceutical Dosage Forms and Drug Delivery Systems, 6.sup.th Ed. p. 199, indicates that excessive blending of lubricants with the granulate ingredients cause water proofing of the granule and reduces tablet hardness or strength of the compressed tablet. For these reasons, high shear mixing conditions have not been used to prepare direct compression dosage forms.
The advantages of direct compression include uniformity of blend, few manufacturing steps involved, (i.e. the overall process involves weighing of powders, blending and compression, hence less cost), elimination of heat and moisture, prime particle dissociation, and physical stability.
In addition to the assignee of the subject application, Biovail Laboratories, current manufacturers of rapidly disintegrating or dissolving solid dose oral formulations include Cima Labs, Prographarm/Ethypharm, R. P. Scherer, and Yamanouchi-Shaklee. All of these manufacturers market different types of rapidly dissolving solid oral dosage forms.
Cima Labs markets OraSolv™, which is an effervescent direct compression tablet purportedly having an oral dissolution time of five to thirty seconds, and DuraSolv™, which is a direct compression tablet having a taste-masked active agent and a purported oral dissolution time of 15 to 45 seconds. Cima's U.S. Pat. No. 5,607,697, for “Taste Masking Microparticles for Oral Dosage Forms,” describes a solid dosage form consisting of coated microparticles that disintegrate in the mouth. The microparticle core has a pharmaceutical agent and one or more sweet-tasting compounds having a negative heat of solution selected from mannitol, sorbitol, a mixture of an artificial sweetener and menthol, a mixture of sugar and menthol, and methyl salicylate. The microparticle core is coated, at least partially, with a material that retards dissolution in the mouth and masks the taste of the pharmaceutical agent. The microparticles are then compressed to form a tablet. Other excipients can also be added to the tablet formulation.
WO 98/46215 for “Rapidly Dissolving Robust Dosage Form,” assigned to Cima Labs, is directed to a hard, compressed, fast melt formulation having an active ingredient and a matrix of at least a non-direct compression filler and lubricant. A non-direct compression filler is typically not free-flowing, in contrast to a direct compression (DC grade) filler, and usually requires additionally processing to form free-flowing granules.
Cima also has U.S. patents and international patent applications directed to effervescent dosage forms (U.S. Pat. Nos. 5,503,846, 5,223,264, and 5,178,878) and tableting aids for rapidly dissolving dosage forms (U.S. Pat. Nos. 5,401,513 and 5,219,574), and rapidly dissolving dosage forms for water soluble drugs (WO 98/14179 for “Taste-Masked Microcapsule Composition and Methods of Manufacture”).
Prographarm/Ethypharm markets Flashtab™, which is a fast melt tablet having a disintegrating agent such as carboxymethyl cellulose, a swelling agent such as a modified starch, and a taste-masked active agent. The tablets have a purported oral disintegration time of under one minute (U.S. Pat. No. 5,464,632).
R. P. Scherer markets Zydis™, which is a freeze-dried tablet having an oral dissolution time of 2 to 5 seconds. Lyophilized tablets are costly to manufacture and difficult to package because of the tablets sensitivity to moisture and temperature. U.S. Pat. No. 4,642,903 (R. P. Scherer Corp.) refers to a fast melt dosage formulation prepared by dispersing a gas throughout a solution or suspension to be freeze-dried. U.S. Pat. No. 5,188,825 (R. P. Scherer Corp.) refers to freeze-dried dosage forms prepared by bonding or complexing a water-soluble active agent to or with an ion exchange resin to form a substantially water insoluble complex, which is then mixed with an appropriate carrier and freeze dried. U.S. Pat. No. 5,631,023 (R. P. Scherer Corp.) refers to freeze-dried drug dosage forms made by adding xanthan gum to a suspension of gelatin and active agent. U.S. Pat. No. 5,827,541 (R. P. Scherer Corp.) discloses a process for preparing solid pharmaceutical dosage forms of hydrophobic substances. The process involves freeze-drying a dispersion containing a hydrophobic active ingredient and a surfactant, in a non-aqueous phase; and a carrier material, in an aqueous phase.
Yamanouchi-Shaklee markets Wowtab™, which is a tablet having a combination of a low moldability and a high moldability saccharide. U.S. patents covering this technology include U.S. Pat. No. 5,576,014 for “Intrabuccally Dissolving Compressed Moldings and Production Process Thereof,” and U.S. Pat. No. 5,446,464 for “Intrabuccally Disintegrating Preparation and Production Thereof.”
Other companies owning rapidly dissolving technology include Janssen Pharmaceutica. U.S. patents assigned to Janssen describe rapidly dissolving tablets having two polypeptide (or gelatin) components and a bulking agent, wherein the two components have a net charge of the same sign, and the first component is more soluble in aqueous solution than the second component. See U.S. Pat. No. 5,807,576 for “Rapidly Dissolving Tablet;” U.S. Pat. No. 5,635,210 for “Method of Making a Rapidly Dissolving Tablet;” U.S. Pat. No. 5,595,761 for “Particulate Support Matrix for Making a Rapidly Dissolving Tablet;” U.S. Pat. No. 5,587,180 for “Process for Making a Particulate Support Matrix for Making a Rapidly Dissolving Tablet;” and U.S. Pat. No. 5,776,491 for “Rapidly Dissolving Dosage Form.”
Eurand America, Inc. has U.S. patents directed to a rapidly dissolving effervescent composition having a mixture of sodium bicarbonate, citric acid, and ethylcellulose (U.S. Pat. Nos. 5,639,475 and 5,709,886).
L.A.B. Pharmaceutical Research owns U.S. patents directed to effervescent-based rapidly dissolving formulations having an effervescent couple of an effervescent acid and an effervescent base (U.S. Pat. Nos. 5,807,578 and 5,807,577).
Schering Corporation has technology relating to buccal tablets having an active agent, an excipient (which can be a surfactant) or at least one of sucrose, lactose, or sorbitol, and either magnesium stearate or sodium dodecyl sulfate (U.S. Pat. Nos. 5,112,616 and 5,073,374).
Laboratoire L. LaFon owns technology directed to conventional dosage forms made by lyophilization of an oil-in-water emulsion in which at least one of the two phases contains a surfactant (U.S. Pat. No. 4,616,047). For this type of formulation, the active ingredient is maintained in a frozen suspension state and is tableted without micronization or compression, as such processes could damage the active agent.
Takeda Chemicals Inc., Ltd. owns technology directed to a method of making a fast dissolving tablet in which an active agent and a moistened, soluble carbohydrate are compression molded into a tablet, followed by drying of the tablets.
Biovail Corporation (the parent of the assignee of the subject application) markets Flash Dose™, which is a direct compression tablet containing a processed excipient called Shearform™. Shearform™ is a floss type substance of mixed polysaccharides converted to amorphous fibers. U.S. patents describing this technology include U.S. Pat. No. 5,871,781 for “Apparatus for Making Rapidly Dissolving Dosage Units;” U.S. Pat. No. 5,869,098 for “Fast-Dissolving Comestible Units Formed Under High-Speed/High-Pressure Conditions;” U.S. Pat. Nos. 5,866,163, 5,851,553, and 5,622,719, all for “Process and Apparatus for Making Rapidly Dissolving Dosage Units and Product Therefrom;” U.S. Pat. No. 5,567,439 for “Delivery of Controlled-Release Systems;” and U.S. Pat. No. 5,587,172 for “Process for Forming Quickly Dispersing Comestible Unit and Product Therefrom.”
One way to provide self-binding flowable formulations is to formulate using Shearform™ matrices or flosses. These matrices result when using certain processing techniques, such as the following: U.S. Pat. No. 5,587,172, incorporated herein by reference, discusses the use of flash heat techniques to produce sucrose-containing shearform flosses, which are then processed to yield quick-dissolving tablets.
The use of shearform matrices for forming comestible units is described in WO95/34290 (published Dec. 21, 1995) from co-assigned PCT application No. PCT/US95/07144, filed Jun. 6, 1995. This case discloses a quick dissolving tablet which is formed by: (1) using flash-flow technology to provide a shearform matrix; (2) combining the partially recrystallized shearform matrix with an additive to form flowable, compactible particulate blends; and (3) compacting the blends at relatively low pressures to produce dosage forms, such as tablets.
Additionally, PCT publication WO 95/34293 (published Dec. 21, 1995) from co-assigned PCT application No. PCT/US95/07194, filed Jun. 6, 1995, discloses a process and apparatus for making rapidly dissolving dosage forms by flash-flow processing. In this PCT application, a shearform matrix is formed by the flash-flow process, the shearform matrix is combined with an additive, and the matrix is molded to make a unit dosage form.
Co-owned U.S. patent application Ser. No. 08/915,068, filed Aug. 20, 1997, now U.S. Pat. No. 5,840,331; and Ser. No. 09/132,986, filed Aug. 12, 1998, now U.S. Pat. No. 6,048,541, describe tablet formulations derived from saccharide-based carriers in which the use of a unique combination of feedstock ingredients yields self-binding, flowable matrices and tablet compositions. This combination—which uses a blend of sugar alcohols, i.e., sorbitol and xylitol—is superior to glycerine in providing cohesive properties and flowability.
Shapeable, preferably tabletable, compositions derived from partially hygroscopic matrices containing these sugar alcohols are useful—in the presence of tableting aids and crystallization promoters—in both high- and low-pressure tableting processes. Tablets and other dosage forms, e.g., lozenges, made therefrom rapidly dissolve when placed in the mouth, generally in less than 30 seconds.
The production of microspheres containing active agent(s) is described in co-owned U.S. Pat. No. 5,683,720, incorporated herein by reference. The patent deals with the use of Liquiflash™ processing to spheronize compositions containing one or more active agents.
Co-owned U.S. Pat. No. 6,165,512 provides compositions and shaped oral dosage forms made therefrom having improved properties. Among those properties are improved processability before shaping and enhanced dissolution and taste-masking properties when the dosage forms are used. The compositions of the '512 patent are based on matrices, or flosses, which comprise at least one sugar alcohol, which matrices are generally considered “single floss” or “unifloss” systems. These systems are exemplified by xylitol-containing shearform matrixes, or flosses, containing a carrier and two or more sugar alcohols.
Various ingredients, such as coated microspheres containing active agent(s), are added, in suitable amounts, to the compositions of the present invention after the matrices are collected and chopped, but before they are shaped, e.g., by tabletting.
Highly useful dosage forms result when microspheres made from compositions containing active agents, solubilizers and spheronization aids are coated with taste-masking agents, then combined with flosses and conventional pharmaceutical ingredients. The resultant tablets enjoy the processing ease associated with the use of glycerine-free flosses and the taste and release properties associated with coated microspheres.
The above mentioned existing quick dissolve technologies present numerous limitations. The above mentioned Prographarm (Ethypharm) dosage forms require relatively high levels of super disintegrant which complicates their use and limits their friability and hardness thereby requiring specialized packaging. Similarly, the Cima dosage forms require effervescent excipients which also reduces their friability and hardness qualities. The R P Scherer, Yamanouchi and Takada technoligies employ complicated processing techniques (i.e. lyophilization, solvents with heat treatment or drying). Those techniques increase the cost associated with the formation of the dosage forms on a large scale.
While Shearform™ matrices are an advance in the art, they also involve an increased cost associated with the processing of the floss matrix which limits their use at a large scale. As well, these amorphous matrices require specialized robotic tableting equipment and generally do not provide friability and hardness properties required for bulk packaging such as in bottles.
As indicated above, disintegrants are often included to ensure that the tablet has an acceptable rate of disintegration. Typical disintegrants include starch derivatives and salts of carboxymethylcellulose. Thus, there still exists a need for non-sticking tabletable compositions which, can be used to make fast-dissolving, pleasant tasting dosage forms at a low cost and without the need for excessive amounts of super disintegrant or complicated processing equipment.